High voltage beaver tail type switch with preinsertion resistor

ABSTRACT

DURING THE FINAL CLOSING MOVEMENT OF A BEAVER TAIL TYPE SWITCH CONDUCTING ARM MEANS EXTENDING RADIALLY FROM NEAR THE DISTAL END OF THE SWITCH BLADE IS SWUNG INTO JUXTAPOSITION WITH TERMINAL CONDUCTOR MEANS CONNECTED TO A RESISTOR ASSEMBLY MOUNTED ON AND TO ONE SIDE OF THE STATIONARY SWITCH CONTACT TO CONNECT THE RESISTOR ASSEMBLY IN SERIES WITH THE SWITCH BLADE AND LIMIT THE INRUSH CURRENT INCIDENT TO CLOSING OF THE SWITCH.

United States Patent I Inventor Joseph Bernatt Arlington Heights, 111.

Appl. No. 772,526

Filed Nov. 1, 1968 Patented June 28. 1971 Assignee S 8: C ElectricCompany Chicago. Ill.

HIGH VOLTAGE BEAVER TAIL TYPE SWITCH WITH PREINSERTION RESISTOR 1 Claim,4 Drawing Figs.

u.s. C1 200/144, ZOO/48A Int. Cl H0111 33/16 200/146,

Field oISearch 146(APR1).48(f0rJ.48(R.P)

[56] References Cited UNITED STATES PATENTS 3,004.1 16 10/1961 Griscom Hr. 200/48 3004.1 17 10/ i961 Skoog1und.... 200/146X 3.121491 3/1964Gorman l.200/48(R)(P)X 3,235,694 2/1966 Thallner 200/144 (APRDX3.291.947 12/1966 Van Sickle ..200/144(APRI)X Primary Examiner Robert K.Schaefer Assistant Examiner- Robert A. Vanderhye Attorney-Robert R.Lockwood ABSTRACT: During the final closing movement of a beaver tailtype switch conducting arm means extending radially from near the distalend of the switch blade is swung into juxtaposition with terminalconductor means connected to a resistor assembly mounted on and to oneside of the stationary switch contact to connect the resistor assemblyin series with the switch blade and limit the inrush current incident toclosing of the switch.

PATENTED JUN28 19m SHEET 1 OF 2 PATENTEU JUN28 l97l SHEET 2 OF 2 HIGHVOLTAGE BEAVER TAIL TYPE SWITCH WITII PREINSERTION RESISTOR Thisinvention constitutes an improvement over the construction disclosed inMikos et al. US. Pat. No. 3,163,736, issued Dec. 29, 1964i It isdesirable to limit the inrush current in'a circuit in energizationthereof. This is particularly the case when a capacitor bank isenergized from a high voltage circuit or a high voltage electric powertransmission line having relatively high capacitance is energized. If.the inrush current is not limited, transient disturbances in the systemmay be generated which may cause flashover, insulation breakdown, andthe like. Further, the closure of the circuit in air may developobjectionable noise incident to formation of arcs on completion of thecircuit.

Accordingly, among the objects of this invention are: To provide a newand improved manner for inserting a resistor in series with a highvoltage switch during closing movement of its switch blade to limit theinrush current incident to completion of the circuit by the switch; tolocate the resistor in such position that it does not interfere with thenormal operation of the switch or the line conductor connected to thestationary switch contact and that it can be applied to a switchconstruction already connected in a high voltage circuit; to apply theresistor insertion assembly to a beaver tail type of switch blade; tomount the resistor assembly on the stationary switch contact to one sideof the plane of pivotal movement of the switch blade; to provideconductor arm means extending radially from near the distal end of theswitch blade for movement into juxtaposition with terminal conductormeans of the resistor assembly to insert the resistor in the circuitduring the closing movement of the switch blade; and to provideflexibility' in the connection between the conductor arm means and theterminal conductor means.

According to this invention, a disconnecting switch construction, suchas that disclosed in the above identified patent, is modified to inserta resistor in the circuit while the switch is being closed for limitingthe inrush current. The switch blade is of the beaver tail type and isarranged to be pivoted about an axis perpendicular to its length towardand away from a cooperating stationary switch contact and also to bepivoted about its longitudinal axis into and out of high pressurecontact engagement with the-stationary switch contact. The resistor,that is inserted in the circuit during the closing movement of theswitch blade, is selected to have the necessary thermal capacity toaccommodate momentarily relatively high current flow that may occur whenthe circuit is closed on a load requiring relatively large current or ona short circuit. The resistor having such capabilities is enclosed in ahousing of porcelain or the like and, at its lower end, is mounted on abracket in offset relation to one side of the stationary switch contact.The upper end of the housing has mounted thereon terminal conductormeans which includes a terminal rod having an intermediatehairpinsection and an elongated depending arcing section that extends inparallel spaced relation to the stationary switch contact. Near thedistal end of the switch blade a conducting arm extends radially and, atits distal end, it carries an arcing finger. As the switch bladeapproaches the switch closed position and before an arc is drawn betweenit and the stationary switch contact, the arcing finger is juxtaposedtothe depending arcing section of the terminal rod. The therebetween is ofthe order of 0.]25 inches with the result that a current conducting arcis formed therebetween and current starts to flow through the resistoras the switch blade continues to swing toward the switch closedposition. The current is limited'. by the resistor and ceases to flowtherethrough when the resistor is shortcircuited on contact engagementof the switch blade with the arcing horns of the stationary switchcontact. During the final closing movement of the switch blade, it isrotated about its longitudinal axis to move laterally extending ribs orthe beaver tail plate section of the switch blade at its distal end intohigh pressure contact engagement with upstanding inverted U-shapedcontact fingers of the stationary switch contact. This movement isaccompanied by corresponding rotation of the conducting arm and archingfinger away from the depending arcing section of the terminal rod. v

In the drawings: FIG. 1 is a top plan view of a switch constructionprovided with resistor inserting means embodying thisinvention. FIG. 2is a a view, in side elevation, of the switch construction shown in FIG.1 FIG. 3 is a view, in side elevation, of the switch blade andstationary switch contact to demonstrate how the conducting arm means isoriented on the switch blade. FIG. 4 is a view, partly in elevation andpartly in section, taken generally along the line 4-4 of FIG. 3.

Referring now particularly to FIGS. 1 and 2 of the drawings, it will beobserved that the reference character 10 designates, generally, switchmeans in which the present invention is embodied. The switch means 10includes a base, indicated generally at 11, that may be formed of a pairof rolled steel channels suitable secured together. Mounted on the base11 are a first insulator 12, a second insulator 13, which is rotatable,and a third insulator 14. The second insulator I3 is rotatably mountedon a bearing 15 that is carried by the base 11 and it has an arm 16extending therefrom for connection to a suitable operating linkage, thatis indicated, generally, at 17. It will be understood that, for threephase operation, three of the switch means 10 are mounted on a suitableswitching structure in proper spaced relation, depending upon thevoltage of the circuit and that suitable operating means, common to theoperating linkage 17, is provided for effecting the simultaneousrotation of the second insulator 13 of each switch means 10 foreffecting simultaneous operation of the three switch means 10 for eitheropening or closing the circuit as may be required.

Extending upwardly from and rotatable with the second insulator 13 is ashaft 18. The shaft 18 extends through and is rotatably mounted on amechanism housing 19. At its upper end the shaft 18 carries a switchcrank 20 which is rotatable therewith. The switch crank 20 is pivotallyconnected to a link 21 that is pivoted at 22 to an arm 23 which extendsfrom a switch blade 24 that forms a part of a disconnecting switch thatin indicated, generally, at 25. The switch blade 24 is pivoted at 26 ona bracket 27 which is carried by one wall of the mechanism housing 19.At its distal end the switch blade 24 is arranged to move into and outof high pressure contact engagement with a line contact member, showngenerally at 28, which is carried by the first insulator 12. It will beunderstood that, on rotation of the second insulator 13 y the operatinglinkage 17, a corresponding rotation of the switch crank 20 is effectedfor swinging the switch blade 24 out of or into high pressure contactengagement with the line' contact member 28, depending upon-thedirection of rotation.

It is desirable that the switch blade 24 be opened only after thecircuit has been opened previously by some other means. The reason forthis is to prevent the drawing of an arc between the distal end of theswitch blade 24 and the line contact member 28 when the circuit isinterrupted under load which might result in damage to these parts or inthe creation of a fault by arcing over to an adjacent phase or toground. For this purpose there is mounted between the mechanism housing19 and a line terminal 31, which is carried by the third insulator 14, acurrent interrupter that is indicated, generally, at 32. Separablecontact means are provided in the current interrupter 32 which areoperated by the mechanism within the mechanism housing 19 under thecontrol of the shaft 18.

The line contact member 28 includes inverted U-shaped contact fingers 33which are suitably mounted on a terminal member 34 from which a lineterminal 35 extends for connection to a line conductor. The terminalmember 34 is suitably mounted on a line contact member support 36 whichis directly supported by the first'insulator 12.

In order to provide for high pressure contact engagement between theswitch blade 24 and'the inverted U-shaped contact fingers 33 the switchblade '24 is provided near its distal end with a beaver tail platesection 37 thatis arranged to enter between the contact fingers 33 at anangle when the switch blade 24 is swung toward the switch close positionabout pivot axis 38 through the pivot 26 on the bracket 27. The pivotaxis 38 is at right angles to the longitudinal axis 39 of the switchblade 24. The closing movement of theswitch blade 24 is arrested when itengages a stop 40 and during the final closing action the switch blade24 is rotated about the longitudinal axis 39 to move the beaver tailplate section 37 to a position at right angles .to the contact fingers33 and thus into high pressure contact engagement therewith.

With a view to preventing arcing between position switch blade 24 andthe contact fingers 33 when the switch blade is swung toward the closedposition, inverted U-shaped arcing fingers 41 are mounted on theterminal member 34 and are arranged to be engaged by an arcing tip 42that projects endwise form the switch blade 24. As the switch blade 24is swung toward the close deposition-it will be understood that thearcing tip 42 approaches the arcing fingers 41 before coming withinarcing distance of the contact fingers 33.

As pointed out above it is likely that there may be a substantial inrushcurrent in the circuit in which the switch means 10 is connected. Thismay be due to the switch closing on a short circuit, closing on acapacitor bank and the like. In order to limit the inrush current aresistor 44 is arranged be connected in series with the circuit andparticularly in series with the switch blade 24 as it is being swungtoward the closed position. The resistor 44 is chosen so as to havesufficient thermal capacity to withstand momentarily current flow thatis likely to take place therethrough on closure of the switch blade 24.The resistor 44 forms a part of a resistor assembly as indicated,generally, at 45 and may be constructed as disclosed in the copendingapplication of John J. Mlkos, Ser. No. 768,825, filed Oct. 18, 1968. Theresistor assembly 45 includes an insulating housing 46 that may beformed or porcelain and it has a lower end terminal 47 and an upper endter minal 48 between which the resistor 44 is connected. A supportplate49, FIG. 1, extends laterally from the lower end terminal 47' andis secured by bolts 50 to a metallic bracket 51 that, in turn, issecured by bolts 52 to line contact member support 36. In this mannerthe lower end terminal 47 is solidly connected to the line contactmember 28. A conductor extension, indicated generally at 53, isconnected to the upper end terminal 48. The conductor extension 53includes a conductor plate 54 that is secured by bolts 55 to the upperend terminal 48. The conductor plate 54 extends angularly and laterallyfrom the upper end of the resistor assembly 45 and has at its distal enda terminal rod that is indicated, generally, at 56 and forms a part ofthe conductor extension 53. The terminal rod 56 has an end section 57that extends into an opening 58 near the distal end of the conductorplate 54 and is secured there by set screws 59. The terminal rod 56 has5 an intermediate .hairpin section 60 which includes a generallysemicircular plan section 61, as indicated in FIG. 1, and an inverted U-shaped section in elevation 62 as shown in FIG. 2. This constructionprovides considerable flexibility in the terminal rod 56. The terminalrod 56 also includes a depending arcing section 63 which is positionedgenerally parallel to the line contact member 28 and is located inspaced relation thereto as indicated in FIG. I.

By positioning the resistor assembly 45 in offset relation with respectto the line contact member 28 or in offset relation with respect to theplane in which the switch blade 24 is pivoted about axis 38, there is nointerference with the operation of the switch blade 24 or with aconductor that may be connected to the line terminal 35. Thus it ispossible to apply the resistor assembly 45 to a switch construction thatis already connected in service in a high voltage transmission line.

In order to place the resistor 44 in circuit with the switch blade 24 asit is being moved toward the closed position conducting arm means,indicated generally at 66, is provided. The conducting ann means 66includes aconducting arm 67 that extends radially from the switch blade24. As shown more clearly in FIG. 4 the conducting arm 67 is secured toa semicircular clamp 68 with which a matingsemicircular clamp 69cooperates to hold the conducting arm 67 in place on the switch blade24. Socket head cap screws 70 interconnect the clamps 68 and 69. Inaddition a set screw 71 extends through the central portion of the clamp69 and into the switch blade 24 in order to position accurately theconducting arm 67 thereon.

Near its distal end contact finger 72 extends radially, from theconducting arm 67 and into overlying relation with the depending arcingsection 63 of the terminal rod 56 when the switch blade 24 is swungtoward the closed position. The contact finger 72 extends through atransverse opening 73 in the conducting arm 67 and is secured inposition therein by a set screw 74. Preferably the relation between thedepending arcing section 63 and the contact finger 72 is such that auniform gap of the order of 0.125 inch as indicated at 75 is providedtherebetween. This insures that the contact finger 72 can move freelywith respect to the depending arcing section 63. The voltage at whichthe switch means 10 ordinarily operates is such that the relativelysmall gap 75 is promptly arched over as the switch blade 24 is movedtoward the switch closed position.

It is desirable that the conducting arm 67 be located accurately on theswitch blade 24 in horizontal to provide the proper relationship betweenthe contact finger 72 and the depending arcing section 63 as the switchblade 24 is swung toward the closed position. This is accomplished bypositioning the conducting arm 67 on the switch blade 24 when the switchblade 24, as indicated in FIG. 3, is at an angle of about l0 from itsfully closed position. When the switch blade 24 is so located, theconducting arm 67 is clamped in position and such that it extendshorizontally or parallel to the base 11, assuming that it is in ahorizontally position. Then the cap screws 70 are tightened and the setscrew 71 is screwed into place to hold positively the conducting arm 67in position on the switch blade 24.

As the switch blade 24 is swung toward the switch closed' position aboutpivot axis 38 on rotation of the switch crank 20 as the result of therotation of the second insulator 13, the beaver tail plate section 37 islocated at an angle of about 30 with respect to the horizontal. Thiscondition is maintained as the switch blade 24 is rotated to theposition shown in FIG. 3 which also is shown in FIGS. 1 and 2. Thisfacilitates entry of the beaver tail plate section 37 between thecontact fingers 33. As the movement of the switch blade 24 continuesabout the pivot axis 38, the distal end of the switch blade 24 engagesthe stop 40. Continued movement of the switch crank 20 effects pivotalmovement of the switch blade 24 about the longitudinal axis 39 toposition the beaver tail plate section 37 substantially horizontal or atright angles to the contact fingers 33. This is accompanied by acorresponding movement of the conducting arm 67 and contact finger 72away from the depending arcing section 63 to the position indicated bybroken lines for the contact finger 72 in FIG. 1.

As soon as the contact finger 72 approaches the upper end of thedepending arcing section 63 of the terminal rod 56 in the closingmovement of the switch blade 24, an arc is established therebetween andcurrent begins to flow through the resistor 44. Because of itsresistance this current flow is limited and there is a correspondingreduction in the inrush current. The closing movement of the switchblade 24 continues with the inrush current being limited by the resistor44. The arcing tip 42 engages the arcing fingers 41 and shortlythereafter the beaver tail plate section 37 engages the contact fingers33 with the result that the resistor 44 is short circuited and currentno longer flows through it.

When the second insulator I3 is rotated in a reverse direction there isa corresponding reverse movement of the shaft 18 and of the switch crank20. The arrangement is such I that, before the switch blade 24disengages the line contact member 28, the current interrupter 32 isoperated to open the circuit under the control of mechanism within themechanism housing 19. Then continued rotation of the lecond insulator 13in an opening direction swings the switch blade 24 out of high pressurecontact engagement with the contact fingers 33 and to an open circuitposition which is substantially at right angles to its switch closedposition. During the final portion of the opening movement of the switchblade 24, the mechanism within the mechanism housing 19 is arranged toreclose the circuit interrupter 32. Thus, in the switch open position,the contacts of the circuit interrupter 32 are closed while the switchblade 24 occupies a generally upright position.

As pointed out above the resistor assembly 45 is offset to one side ofthe line contact member 28. In addition it is inclined away from theline contact member 28 in order to permit the construction of theterminal rod 56 with substantial flexibility between-the upper end ofthe resistor assembly 45 and the depending arcing section 63.

I claim:

1. A resistor inserting switch construction having a stationary switchcontact and a cooperating switch blade pivoted about an axisperpendicular to its longitudinal axis for movement toward and away fromsaid stationary switch contact, said switch construction beingcharacterized by a resistor assembly mounted at one end to one side ofthe plane of pivotal movement of said switch blade on said stationaryswitch contact and electrically connected thereto,

terminal conductor means connected to and extending from the other endof said resistor assembly with its distal end forming an arcing sectiondisposed in offset generally parallel relation to said stationary switchcontact,

conducting arm means carried by and extending radially from said switchblade near its distal end and arranged to be moved into juxtaposition tosaid arcing section of said terminal conductor and form a currentconducting arc therebetween to connect said resistor assembly in serieswith said switch blade as it is swung to switch closed position withsaidstationary switch contact, and

means pivotally mounting said switch blade about its longitudinal axisfor movement at its distal end into high pressure contact engagementwith said stationary switch contact and swinging said conducting armmeans away from said arcing section while said switch blade is pivotinginto said high pressure contact engagement.

